Until recently, cathode-ray tubes (CRTs) have been typically used as a display device. More recently, liquid crystal display (LCD) devices have been the subject of research and development because of their superior visibility, low power consumption and low heat emission as compared with the CRTs. Accordingly, the LCD devices with another flat panel display such as plasma display panels (PDPs) and field emission displays (FEDs) have been widely used as a next generation display device for a cellular phone, a monitor and a television.
LCD devices use optical anisotropy and polarization properties of liquid crystal molecules of a liquid crystal layer to produce an image. The liquid crystal molecules have long and thin shapes, and because of the optical anisotropy property, the polarization of light varies with the alignment direction of the liquid crystal molecules. The alignment direction of the liquid crystal molecules can be controlled by varying the intensity of an electric field applied to the liquid crystal layer. Accordingly, a typical LCD device includes two substrates spaced apart and facing each other and a liquid crystal layer interposed between the two substrates. Each of the two substrates includes an electrode on a surface facing the other of the two substrates. A voltage is applied to each electrode to induce an electric field between the electrodes and the arrangement of the liquid crystal molecules as well as the transmittance of light through the liquid crystal layer is controlled by varying the intensity of the electric field, thereby displaying images.
Since LCD devices are non-emissive type display devices, a light source is required to display images. A backlight unit is disposed under a liquid crystal panel and light from the backlight unit is supplied to the liquid crystal panel. As a result, the light transmittance is controlled by the alignment of the liquid crystal molecules to display images.
FIG. 1 is a plan view showing a multi-vision display device according to the related art. The multi-vision display device includes at least two independent LCD devices coupled with each other. In FIG. 1, a multi-vision display device 5 includes four liquid crystal display (LCD) devices 80 disposed in matrix. The four LCD devices 80 display different images or equal images, respectively, to display various images. Alternatively, the four LCD devices 80 display four partial images that constitute a single image. The multi-vision display device 5 further includes a frame 72, an upper supporting means 70 and a lower supporting means (not shown). The frame 72 has a rectangular ring shape and the four LCD devices 80 are disposed on the frame 72 to be separated from each other. The upper supporting means 70 and the lower supporting means are formed by a press process. The upper supporting means 70 corresponds to gaps between the four LCD devices 80 to support the four LCD devices 80 at an upper position. An active area AA of the multi-vision display device 5 is defined by an image display region of the four LCD devices 80. The four LCD devices 80 are coupled to form the multi-vision display device 5 using a coupling means T having a plurality of screws 90 in a non-active area NAA corresponding to a boundary portion of the frame 72 and a space between the four LCD devices 80.
FIGS. 2A and 2B are cross-sectional views showing an exemplary coupling portion and another exemplary coupling portion, respectively, for a multi-vision display device according to the related art. In FIG. 2A, the coupling means T includes a screw 90. Upper and lower supporting means 70 and 15 are spaced apart from each other and a middle supporting means 60 is disposed between the upper and lower supporting means 70 and 15. The upper, middle and lower supporting means 70, 60 and 15 are combined with each other by the screw 90. The upper, middle and lower supporting means 70, 60 and 15 have a through hole 85 having a cylindrical shape, and a screw thread is formed on a side surface of the through hole 85 of the middle and lower supporting means 60 and 15. For strong fixation, the lower supporting means 15 further has a protrusion F corresponding to a circumference of the through hole 85, which is referred to as a boss-processed structure. In FIG. 2B, the lower supporting means 15 has a bent protrusion H corresponding to a circumference of the through hole 85 for stronger fixation, which is referred to as an emboss-processed structure. In FIGS. 2A and 2B, each of the protrusion F and the bent protrusion H has elasticity to fix the screw 90 strongly.
Although the strong fixation is obtained in the multi-vision display device 5, the boss-processed structure or the emboss-processed structure requires a sufficient area. For example, when the multi-vision display device 5 has the through hole 85 having a first diameter B1, the boss-processed structure of FIG. 2A may require an area corresponding to a second diameter B2 greater than the first diameter B1 on the basis of the middle supporting means 60 and the protrusion F, and the emboss-processed structure of FIG. 2B may require an area corresponding to a third diameter B3 greater than the first diameter B1 on the basis of the middle supporting means 60 and the bent protrusion H. As a result, each of the boss-processed structure and the emboss-processed structure requires a greater area than the screw 90 corresponding to the first diameter B1. Specifically, although the emboss-processed structure has an advantage in strong fixation, the emboss-processed structure requires a greater area for the screw 90 than the boss-processed structure.
In the multi-vision display device 5 having the active area AA and the non-active area NAA, reduction of the non-active area NAA is necessary to increase the active area AA. However, there is a limitation in reduction of the non-active area NAA, i.e., reduction in a width X of the non-active area NAA, because the structure for fixation of the four LCD devices 80 to the upper, middle and lower supporting means 70, 60 and 15 requires the greater area than the screw 90.